The present invention relates to a cutting tool and in particular to a grooving or parting-off tool having a removable insert. More particularly, the invention is concerned with a parting-off tool in which an insert is retained securely within the parting-off tool without need for special clamping devices.
Parting-off tools using removable inserts are well known. In particular, U.K. Pat. No. 1,379,637 describes a cutting tool, for example, a parting or groove cutting tool having a plate-like holder. An integral arm is adapted to clamp a cutting insert within the holder, the clamping pressure on the cutting insert resulting from bending of the arm. A surface on the arm presses against one face of the insert while other faces of the insert engage surfaces on the holder. The insert may be released from or inserted into the holder when the arm is urged away from the insert by inserting an elliptical section rod in a slot portion. The elliptical section rod acts as a cam on turning which opens the arm and reduces pressure against the face of the insert. The disadvantage of the groove cutting tool of U.K. Pat. No. 1,379,637 is that the clamping pressure results solely from the bending of the arm. During groove cutting, extreme forces are applied to the insert which causes the arm to open allowing the insert to move within the holder.
U.K. patent application Ser. No. 2,064,390A describes a rotary cutting tool using a cutting element peripherally disposed on a disc. Each of the cutting elements frictionally engages the surface in the disc formed in a "V" shape. A problem with cutting tools of this type is that the jaws retaining the cutting insert are opened by the forces on the insert pushing the cutting insert into the "V". While this may not be significant on a rotary saw which is constantly advancing, it presents problems in fine machine grooving and parting off.
In U.K. Pat. No. 2,082,485 there is described a cut-off tool having a support blade with upper and lower jaws shaped for receiving an insert. The upper jaw 108 is flexible and provides the clamping means on the insert. A second aperture is positioned in the support blade such that the upper jaw is bound by the upper apertures and remains flexible. An actuating member is mounted in an opening which communicates with the second aperture such that a camming action causes the upper jaw to clamp the top surface of the insert. This arrangement overcomes some of the problems which are posed by the integral arm clamping means of U.K. Pat. No. 1,379,637. However, movement of the actuating member can cause shifting of the clamping member on the insert, particularly if the actuating member becomes worn or is badly fitted into the cutting tool.
Cutting inserts are retained in a holder for rotary tools in U.K. patent application Ser. No. 2,110,136A and in European patent application Ser. No. 0,059,602, by the geometrical characteristics of the holder and the insert, by means appearing identical to the retention system disclosed in U.K. patent application Ser. No. 2,064,390A. The holder includes jaw-like seats for the inserts wherein the contour of the seat matches the contour of the tool holder, and there is no clamping means requiring a minimum thickness of the holder or taking up valuable space on the periphery of the tool. The geometry which is responsible for retaining the cutting insert in the holder in these prior art devices, includes the substantially wedge shape of the inserts with prismatic or multiple plane retaining surfaces and the matching wedge shaped surfaces, respectively, of the seats. In these prior art patent applications, the inserts are located in the seats in the tool holder by means of an insertion force, and the inserts are not retained by external clamps, but instead by "wedge" forces. Although convex/concave or concave/convex shapes of the retaining surfaces of the seats and the inserts may provide some stability of the insert in the tool with respect to side forces, it is desirable to improve the stability to all forces and to simplify the means for retaining inserts in blades for cutting tools.